Phase compensation for multi-stimulus controller

• US 20100060593A1
• Filed: 09/10/2008
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Krah, Christoph H.
• Granted Patent: US 8,237,667 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Determining a compensated phase matrix for a multi-stimulus demodulation process is provided. A first drive line of a multi-stimulus sensing system is selected, and a stimulation signal is transmitted on the selected drive line. A channel gain resulting from the stimulation signal is measured from a received sense signal resulting from the stimulation signal. The measured channel gain is compared with a known channel gain to obtain an individual phase compensation for the selected drive line. A compensated phase matrix is formed of the individual phase compensation values for multiple drive lines.

Claims

1. A method of determining a compensated phase matrix for a multi-stimulus demodulation process, the method comprising:

measuring individual phase delays of each drive line and sense line combination of a multi-stimulus sensing system; and

forming the compensated phase matrix based on the individual phase delays.

2. The method of claim 1, wherein measuring the individual phase delays comprises:

stimulating a first drive line with a first stimulation signal;

receiving, at a first receive channel, a first sense signal resulting from the stimulation signal; and

determining the individual phase delay of the first drive line and first sense line pair.

3. The method of claim 2, wherein determining the individual phase delay of the first drive line and first sense line pair comprises:

demodulating the first sense signal to obtain a measurement of phase delay; and

adjusting an adjustable delay value such that the measurement of phase delay is maximized, wherein the individual phase delay is based on the value of the adjustable delay at the maximum measurement of phase delay.

4. The method of claim 1, wherein measuring the individual phase delays comprises:

stimulating a first drive line with a first stimulation signal;

receiving, at a plurality of receive channels, sense signals resulting from the stimulation signals; and

determining the individual phase delays of each pair of first drive line and corresponding sense line.

5. The method of claim 4, wherein determining the individual phase delay of each pair of the first drive line and a corresponding sense line comprises:

demodulating the corresponding sense signal to obtain a measurement of phase delay;

adjusting an adjustable delay value such that the measurement of phase delay is maximized for a particular pair of the first drive line and corresponding sense line, wherein the individual phase delay for that particular pair is based on the value of the adjustable delay at the maximum measurement of phase delay; and

repeating the adjusting of the adjustable delay for the pairs of the first drive line and other sense lines to obtain corresponding individual phase delays.

6. A method of determining a phase adjusted decode matrix for a multi-stimulus demodulation and decode process, the method comprising:

selecting a first drive line and first channel;

transmitting a stimulation signal on the selected drive line;

adjusting the first channel phase until the demodulated signal becomes maximum, and recording the adjusted phase at the maximum;

repeating the selecting, transmitting, and adjusting for other combinations of drive lines and sense lines to determine corresponding other phases;

determining phase adjustments for all channels based on the determined phases; and

forming the phase adjusted decode matrix based on the phase adjustments.